Soy foods in cardiovascular disease

Several studies have shown that the addition of soy foods or extracts to the diet lowers cholesterol. In a 1997 study, 17 healthy men and 17 healthy women with raised levels of total and LDL cholesterol were given either 2 per cent cows' milk products, soybean products or a combination of skim milk products and soy oil, over period of four weeks. During the soybean period, the subjects' mean level HDL cholesterol increased 9 per cent and their mean LDL/HDL cholesterol ratio decreased 14 per cent. Soy compounds may also reduce the oxidation of LDL cholesterol and inhibit clumping together of platelets, both of which slow the atherosclerotic process. They may also improve arterial function.

Soy foods in cancer

Eating soy foods may lower the risk of cancers, particularly those that are hormone-dependent, such as breast and prostate cancer. Breast cancer rates are lower in countries with soy-based diets and soy products have been shown in many animal experiments to inhibit tumor growth. Genistein may block the stimulatory effect of estrogen on cancer cells. Other hormone-dependent cancers, such as prostate cancer, may also be affected by genistein, which appears to block enzymes that promote tumor growth. Genistein may also inhibit the growth of new blood vessels into tumors.

Researchers involved in a study published in 1997 examined the links between soy and endometrial cancer in 332 women diagnosed with endometrial cancer from various ethnic groups in Hawaii. Their diets were compared with 511 control subjects. High consumption of soy foods and other legumes was associated with a decreased risk of endometrial cancer, with those in the high intake group having around half the risk of those in the low intake group. A 1996 US study showed a decrease in breast cancer risk in Asian American women who increased tofu intake.

Soy foods in menopause and osteoporosis

Japanese women appear to suffer fewer menopausal symptoms than Western women. One of the reasons may be their high consumption of soy foods. Soy foods may also be useful in preventing osteoporosis which occurs when a decline in circulating estrogen leads to a reduction in bone mass. Estrogen-like compounds such as genistein can help to build bone.

In a 1998 double-blind, randomized placebo-controlled study Italian researchers investigated the effects of daily dietary supplementation of soy protein isolate powder on hot flashes in 104 postmenopausal women. Fifty-one patients took 60 g of isolated soy protein daily and 53 took 60 g of placebo daily. The study lasted 12 weeks. The results showed that soy was much better than placebo at reducing the average number of hot flashes per 24 hours after four, eight, and 12 weeks of treatment. By the end of the twelfth week, women taking soy had a 45 per cent reduction in their daily hot flashes versus a 30 per cent reduction obtained with the placebo.